Analog baseband filtering apparatus of multimode multiband wireless transceiver and control method thereof

ABSTRACT

The ABB blocks  332, 334, 336,  and  318  are configured to process the I/Q signals corresponding to the first or the second HB independently or the I/Q signals corresponding to the LB in cooperation by two. In detail, the first ABB I block  332  and the first ABB Q block  334  operate independently in the 3G/4G mode but they are configured to process the I signal (or Q signal) of the LB in the 2G mode. Likewise, the second ABB Q block  336  and the second ABB I block  318  operate independently in the 3G/4G mode but they are configured to process the Q signal (or I signal) of the LB in the 2G mode. The first ABB I/Q blocks  332  and  334  and the second ABB I/Q blocks  336  and  318  are arranged symmetrically to processing the I/Q signals cooperatively in the 2G mode. In detail, the second ABB Q block  336  is arranged close to the first ABB Q block  334  such that the capacitor regions included in the first ABB I/Q blocks  332  and  334  are connected to each other and the capacitor regions included in the second ABB I/Q blocks  336  and  338  are connected to each other.

TECHNICAL FIELD

The present invention relates to a wireless communication system and, inparticular, to a filtering apparatus of a multimode multibandtransceiver for filtering a signal carrying an analog baseband signaland a control method thereof.

BACKGROUND ART

A wireless communication receiver uses an analog filter to select thesignal of the intended channel by removing unnecessary noise from thesignal demodulated to baseband by a mixer. The accurate cutoff frequencyconfiguration for the analog filter exerts significant influences to thesystem performance.

Typically, a filter has an input-to-output gain varying, as thefrequency increases, and is provide with a pass band and a stop band.The term ‘cutoff frequency (fc)’ denotes a boundary frequency betweenthe pass band and the stop band. In the case of Low Pass Filter (LPF),the cutoff frequency (fc) is defined as a frequency having a gain whichis 3 dB lower than then gain of the direct current or low frequency inthe pass band. The cutoff frequency (fc) is determined by a feedbackresister and a feedback capacitor used in the analog filter.

The baseband covers a very broad range including 100 kHz bandwidth forthe 2nd Generation (2G) communication system and 20 MHz bandwidth forthe 3rd Generation (3G) and 4th Generation (4G) communication system,and the broadest bandwidth is about 100 times the narrowest one. Amultimode mobile terminal designed to operate in a 2G mode for voicecommunication and in a 3G or 4G mode (hereinafter, referred to as 3G/4Gmode) has to have a multimode multiband radio transceiver equipped withan analog baseband filter capable of supporting various bandwidths asaforementioned.

However, since the resistance and capacitance values determining thecutoff frequency of the analog baseband filter vary depending on thetemperature and process conditions and are difficult to estimateaccurately, the cutoff frequency is likely to differ from the targetvalue in the real environment. Accordingly, the cutoff frequency iscompensated by controlling a variable resister or a variable capacitorusing a digital algorithm under the condition that the error has to bewithin the range of 4%.

Since the cutoff frequency is inversely proportional to the resistanceand the capacitance, there is a need of the resistor having a largeresistance and the capacitor having a large capacitance to process thelow band signal of the legacy system such as 2G system. The capacitorfor processing the low band signal of the 2G system is a few timeslarger in size than that for processing the 3/4G band signal and thusincreases the circuit area of the analog filter. This means that thecircuit area of the analog filter increases due to the disabled 2G modein the state that the 3/4G mode is enabled, resulting in increase ofmanufacturing costs. The increased circuit area also elongates the wirelength so as to increase signal error and noise, resulting indegradation of signal characteristics.

DISCLOSURE OF INVENTION Technical Problem

The present invention provides an analog signal filtering apparatus of aradio transceiver and a control method thereof.

Also, the present invention provides a variable gain amplifier and avariable frequency filter capable of processing various frequency bandssignals in a single structure.

Also, the present invention provides an analog signal filteringapparatus having an analog baseband filter of which circuit area isminimized for use in multimode multiband environment and a controlmethod thereof.

Also, the present invention provides an analog signal filteringapparatus of a multimode multiband radio transceiver that is capable ofsharing capacitor on a diversity pass and enhancing the input andfeedback resisters structures and a control method thereof.

Also, the present invention provides an analog signal filteringapparatus of a multimode multiband receiver that is capable of using aplurality of concatenated analog baseband filters and a control methodthereof.

Furthermore, the present invention provides an analog signal filteringapparatus of a multimode multiband receiver that is capable of supportCarrier Aggregation (CA) and a control method thereof.

Solution to Problem

In accordance with an aspect of the present invention, a filteringapparatus of a multimode multiband radio transceiver is provided. Thefiltering apparatus includes a filtering unit which filters RadioFrequency (RF) signals on one of at least one frequency bands, aswitching unit which switches the signals among at least one filterblock included in the filtering unit according to a selectedcommunication mode, and a controller which selects the communicationmode and controls the switching unit.

In accordance with another aspect of the present invention, a method forcontrolling a filtering apparatus of a multimode multiband radiotransceiver is provided. The method includes receiving, at a filteringunit including at least one filter block, Radio Frequency (RF) signal onat least one frequency bands, determining a communication mode based onthe received signal, switching the signal among at least one filterblock included in the filtering unit according to the communicationmode, and filtering and amplifying, at the filtering unit, the signal.

Advantageous Effects of Invention

The analog signal filtering apparatus and method of the presentinvention is advantageous in terms of providing a variable gainamplifier, filter circuit, and algorithm capable of fulfilling the gainsand bandwidths required by the baseband receiver for all mobilecommunication standards complied by 2G, 3G, and 4G systems.

Also, the analog signal filtering apparatus and method of the presentinvention is advantageous in terms of implementing the various circuitstructures capable of decreasing manufacturing costs and enhancing noisecancellation by decreasing the circuit area as compared to theconvention technologies and facilitating application of Multiple InputMultiple Output (MIMO) receiver configurations such as 4×2, 4×4, and 8×4antenna configurations.

Also, the analog signal filtering apparatus and method of the presentinvention is advantageous in terms of providing a filter circuit forcommunication circuit design supporting Carrier Aggregation (CA) for useof carriers on multiple frequency bands.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a circuit diagram illustrating a configuration of an analogfilter having a characteristic function of the first order filter;

FIGS. 2A and 2B are a block diagram and a floor plan diagramillustrating the analog baseband filter;

FIG. 3A is a block diagram illustrating a configuration of a receiversupporting a plurality HB modes according to an embodiment of thepresent invention;

FIG. 3B is a diagram illustrating a configuration of the terminalsupporting the first and second HB modes according to an embodiment ofthe present invention;

FIGS. 4A and 4B are a block diagram and a floor plan diagramillustrating the analog baseband filter according to an embodiment ofthe present invention;

FIGS. 5A to 5C are diagrams illustrating the mode switching of theanalog filter according to an embodiment of the present invention;

FIG. 6 is a circuit diagram illustrating a resister block varying inresistance depending on the operation mode according to an embodiment ofthe present invention;

FIGS. 7A to 7F are circuit diagrams illustrating various configurationsof the resistor block according to an embodiment of the presentinvention;

FIG. 8 is a circuit diagram illustrating a configuration of the analogbaseband filter according to an embodiment of the present invention;

FIGS. 9A and 9B are circuit diagrams illustrating detailed arrangementof the capacitors according to an embodiment of the present invention;and

FIGS. 10A to 10C are diagrams illustrating the operation mechanisms ofthe filter according to an embodiment of the present disclosure.

MODE FOR THE INVENTION

Exemplary embodiments of the present invention are described withreference to the accompanying drawings in detail.

Detailed description of well-known functions and structures incorporatedherein may be omitted to avoid obscuring the subject matter of thepresent invention. This aims to omit unnecessary description so as tomake the subject matter of the present invention clear.

For the same reason, some of elements are exaggerated, omitted orsimplified in the drawings and the elements may have sizes and/or shapesdifferent from those shown in drawings, in practice. The same referencenumbers are used throughout the drawings to refer to the same or likeparts.

Detailed description of well-known functions and structures incorporatedherein may be omitted to avoid obscuring the subject matter of thepresent invention. Further, the following terms are defined inconsideration of the functionality in the present invention, and mayvary according to the intention of a user or an operator, usage, etc.Therefore, the definition should be made on the basis of the overallcontent of the present specification.

The present invention is not limited by exemplary embodiments providedin the drawings and the specification. Throughout the drawings, likereference numerals refer to like members. The drawings have beensimplified and relatively exaggerated to emphasize the features of thepresent invention, and dimensions in the drawings do not accuratelymatch the dimensions of actual products of the present invention. Thoseof ordinary skill in the art may easily modify dimensions, such aslength, circumference, and thickness, of each component from thedisclosure of the drawings for application into an actual product, andit will be obvious to those of ordinary skill in the art that suchmodification falls within the scope of the present invention.

The following embodiments of the present invention relates to an analogfilter for filtering analog signal and, in particular, to a multimodemultiband analog baseband filter. The Analog Baseband (ABB) filter maybe used for a radio transceiver supporting radio communicationtechnologies with various bandwidths such as Global System for Mobilecommunications (GSM), Enhanced Data GSM Environment (EDGE), High SpeedPacket Access (HSPA). Wideband Code Division Multiple Access (WCDMA),Long Term Evolution (LTE) 1.4M, LTE 3M, LTE 5M, LTE 10M, LTE 15M, andLTE 20M.

FIG. 1 is a circuit diagram illustrating a configuration of an analogfilter having a characteristic function of the first order filter.

Referring to FIG. 1, the analog filter 100 includes an OperationalAmplifier (OP AMP) 150 which receives the input voltage Vin through itsnegative terminal via the input resistor Ra 160 and of which positiveterminal is grounded, a feedback resister Rb 170 connecting the negativeinput terminal of the OP AMP 150 and the output terminal Vout of theanalog filter 100 in parallel, and a feedback capacitor C 180. Theresistors 160 and 170 and variable registers of which resistances can bevaried to adjust the gain and cutoff frequency of the analog filter 100.The gain and cutoff frequency of the direct current of the analog filter100 are expressed as equation (1):Gain:R_(b)/R_(a),f_(c):1/(2πR_(b)C)  (1)

In equation (1), Ra denotes the resistance of the input resistor 160, Rbdenotes the resistance of the feedback resistor 170, and C denotes thecapacitance of the feedback capacitor 180. The cutoff frequency isinversely proportional to the feedback resistance Rb and the feedbackcapacitance C. Here, the Rb and C have the characteristics of increasinglinearly or exponentially under the control with a digital code.

The reception filter applicable to a Radio Frequency (RF) circuit isimplemented as a 3 to 7-stage filter by combining in series a Real Pole(RP) filter having one RP and a plurality of (e.g. 2 to 6) bi-quad (BQ)filter(s) having one or more RPs.

The baseband covers diverse bandwidths including 100 kHz bandwidth forthe 2G system such as GSM and 10 MHz bandwidth for the 4G system such asLTE. Table 1 shows the examples of cutoff frequencies for standardizedmobile communication basebands.

TABLE 1 3G Stan- 2G HSPA HSPA 4G dard GSM EDGE SC DC LTE1.4 LTE3 LTE5LTE10 LTE15 LTE20 Band- 100 100 1.92 4.42 615 1.5 2.5 5 7.5 10 width kHzkHz MHz MHz kHz MHz MHz MHz MHz MHz

Here, HSPA SC denotes Single Carrier HSPA, and HSPA DC denotes DualCarrier HSPA. In the 3G/4G mode, it is possible to use extra frequencyband for diversity with additional receive antennas as well as thefrequency band for basically used receive antenna. In the presentinvention, the two frequencies are referred to as primary (PRX) HighBand (HB) and diversity (DRX) HB.

FIGS. 2A and 2B are a block diagram and a floor plan diagramillustrating the analog baseband filter.

Referring to FIG. 2A, the analog baseband filter includes the first andsecond filtering and amplifying paths 210 and 215 for In phase (I)signal and Quadrature phase (Q) signal of the 3G/4G mode PRX HB, thethird and fourth filtering and amplifying paths 220 and 225 for I and Qsignals of the 3G/4G mode DRX HB, and the fifth and sixth filtering andamplifying paths 230 and 235 for I and Q signals of the 2G mode Low Band(LB).

Each of the filtering/amplifying paths 210 to 235 forms an I/Q chain forfiltering and amplifying (hereinafter, referred to asfiltering/amplifying) the I or Q signal. In detail, the firstfiltering/amplifying path 210 includes a RP filter 202 connected to thepositive input (IP) and negative input (IN) of the I signal of the PRXHB, a first BQ filter 204, a second BQ 206, and a Variable GainAmplifier (VGA) 208 connected to an IP output (OIP) and an IN Output(OIN). The RP filter 202, the first and second BQ filters 204 and 206,and the VGA 208 are connected in series. Like the firstfiltering/amplifying path 210, the second filtering/amplifying path 215includes three filters and VGA, receives the input of QP and QN, andoutputs OQP and OQN. Likewise, each of the other filtering/amplifyingpaths 220 to 235 includes three filters and VGA connected in series.

FIG. 2B is a floor plan diagram illustrating the circuit correspondingto the analog baseband filtering/amplifying paths 210 to 235 of FIG. 2A.The drawing shows the connection relationship between thefiltering/amplifying paths 210 to 235 and the RF units inputting I/Qsignals to the filtering/amplifying paths 210 to 235 and internalarrangements of the respective filtering/amplifying paths 210 to 235.

Referring to FIG. 2B, the PRX RF I unit 242 receives the RF signal ofthe PRX HB, converts the signal to a baseband I signal, and sends the Isignal to the first filter block 260 and 262 which is equivalent to thefirst filtering/amplifying path 210 of FIG. 2A. The PRX RF Q unit 244receives the Q signal of the PRX HB and sends the Q signal to the secondfilter block 264 and 266, the DRX RF I unit 246 receives the I signal ofthe DRX HB and sends the I signal to the third filter block 268 and 270,and the DRX RF Q unit 248 receives the Q signal of the DRX HB and sendsthe Q signal to the fourth filter block 272 and 274. Likewise, thefilter block 264 to 274 are equivalent to the second to fourthfiltering/amplifying paths 215 to 225 of FIG. 2A.

The 2G RF Q unit 250 receives the RF signal of the 2G LB, down-convertsthe RF signal to the baseband Q signal, and sends the Q signal to thefifth filter block 276 and 278 which is equivalent to the fifthfiltering/amplifying paths 230 of FIG. 2A. The 2G RF I unit 252 receivesthe RF signal of the 2G LB, down-converts the RF signal to the basebandI signal, and sends the I signal to the sixth filter block 280 and 282which is equivalent to the sixth filtering/amplifying path 235 of FIG.2A.

The devices constituting the filter block 210 of FIG. 2A are classifiedinto passive devices such as resistors and capacitors and active devicessuch as OP AMP. The first filter block includes the capacitor region 260including capacitor banks and resistors and an active region 262including the OP AMPs. Likewise, the second to sixth filter blocks 2640to 282 include the respective capacitor regions 266, 268, 274, 276, and282 and the respective active regions 264, 270, 272, 278, and 280. Forfacilitating circuit fabrication, it is typical that the adjacent filterblocks are configured such that the identical regions are positionedclosely. For example, the active region of the first filter block isarranged close to the active region of the second filter block, thecapacity region 266 of the second filter block close to the capacitorregion 268 of the third filter block, and the active region 270 of thethird filter block close to the active region 272 of the fourth filterblock. Likewise, the capacitor region 274 of the fourth filter block isarranged close to the capacitor region 276 of the fifth filter block forthe 2G mode, and the active region 278 of the fifth filter block closeto the active region 280 of the sixth filter block. That is, the I and Qpaths of each band are arranged symmetrically on the floor plan.

As described above, since the cutoff frequency is inversely proportionalto the product of the resistance and capacitance, there is a need of aresistor having a very large resistance and a capacitor having a verylarge capacitance to process the low band signal of legacy system suchas 2G system and, as a consequence, the circuit areas of the capacitorregions 276 and 282 of the fifth and sixth filter blocks for the 2G modeare very large as compared to the capacitor regions 260, 266, 268, and274 for the 3G/4G mode. Depending on the embodiment, the filter blocksfor the 2G mode may be about two times larger in area than the filterblocks for the 3G/4G mode.

If the diverse ranges of the baseband are processed by controlling theresistances of the resistors instead of using the capacitors occupyinglarge area, this makes it possible to decrease the circuit area butcauses a problem of increasing the noise. In detail, the noise occurringin the real wireless environment is proportional to the input resistanceof the first filter 202 as shown in equation (2) and multiplied with thegain to be reflected the output signals of OIP and OIN.V _(N) ²=4kTR·BW  (2)

In equation (2), V_(N) denotes noise voltage, k denotes Boltzmannconstant (=1.38*10⁻²³ J/K), T denotes absolute temperature, R denotesinput resistance of the first filter 202, and BW denotes bandwidth.

The Noise Figure required for the analog baseband filter is equal to orless than 30 dB and corresponds to the noise occurring with theresistance of 50 kΩ which is 1000 times larger than the referenceresistance of 50Ω. Accordingly, the input resistance of each filtercannot be equal to or greater than 50 kΩ. Also, since the gain of eachfilter is in the range of 0 to 24 dB (1˜16 times), the feedback resisterhas the resistance of 1/16˜1 the input resistance and requires thefrequency ranges 100 times larger for processing the bandwidths of the2G and 4G systems as described above and thus the 1600 times large gainrange is required to achieve the intended cutoff frequency only throughcontrolling the resistance. Also, in order to achieve the 24 dB gain inthe course of using the input resistor of 500Ω which is 1/100 themaximum resistance of 50 kΩ of the input resister, the feedback resisterhas to have the resistance of at most 31.255 and thus the outputimpedance drops significantly, resulting in failure of achieving theintended gain and deterioration of signal distortion.

The following embodiment of the present invention proposes an analogbaseband filter circuit capable of using the signal chains for thefrequency bands of the High Band (HB) mode in the Low Band (LB) mode. Inan example, the Q channel signal paths for the PRB HB and DRX HB of theHB mode are shared for use in the LB mode. In another example, the Ichannel signal paths for the PRB HB and DRX HB of the HB mode are sharedfor use in the LB mode.

FIG. 3A is a block diagram illustrating a configuration of a receiversupporting a plurality HB modes according to an embodiment of thepresent invention.

Referring to FIG. 3A, the receiver includes a plurality of RF units 302,304, and 306 for processing HB or LB signals; a plurality of analogbaseband (ABB) blocks 312, 314, and 316 for processing baseband signals;a switching unit 310 for connecting the RF units 302, 304, and 360 andthe ABB blocks 312, 314, and 316 selectively; and a control unit 300 forcontrolling the switching unit 310 according to the selectedcommunication mode.

The RF units 302, 304, and 306 perform RF processing for I or Q path ofthe frequency band according to the selected communication mode. In anembodiment, the first RF unit 302 is configured to process the first HBsignal and the LB signal, converts the received HB RF signal to basebandI or Q signal in the HB mode, and converts the received LB RF signal toI or Q signal in the LB mode.

Each of the ABB blocks 312, 314, and 316 is configured to process thebaseband signal corresponding to the respective HBs or to process thebaseband signal corresponding to the LB in cooperation with neighboringABB block. In an example, the first and second ABB blocks 312 and 314operate independently in the HB mode but are concatenated in the LB modeto process the LB signals. Depending on the embodiment, the first andsecond ABB blocks 312 and 314 are arranged symmetrically to processingthe LB signals together. In detail, the capacitor region of the firstABB block 312 is arranged close to the capacitor region of the secondABB block 314 such that the capacitor regions of the first and secondABB blocks 312 and 314 are connected to each other in the LB mode.According to an embodiment, the first and second ABB blocks 312 and 314are connected such that the combined capacitance increases inproportional to the each of the capacitances of the capacitors.

The switching unit 310 connects the RF units 302, 304, and 306 to theABB blocks 312, 314, and 316 selectively according to the selectedcommunication mode under the control of the control unit 300. Thecontrol unit 300 manages the overall operations of the receiver andcontrols the switching unit 310 depending on whether the communicationmode is the LB mode or the HB mode. In detail, the switching unit 310connects the first RF unit 302 to the first ABB block 312, the second RFunit 304 to the second ABB block 314, and the N_(th) RF unit 306 to theN_(th) ABB block.

In the LB mode, if the first RF unit 302 is configured to receive the LBRF signal, the switching unit 310 connects the first RF unit 302 to thesecond ABB block 314, and the capacitor region of the second ABB block314 is extended to include the capacitor region of the first ABB block312. For this extension, the capacitor region of the second ABB block314 is arranged close to the capacitor region of the first ABB block 312such that the two capacitor regions are concatenated to process (filterand amplify) the baseband signal corresponding to the LB. Likewise, atleast two other ABB blocks may be connected to different RF units toprocess the baseband signal of the LB.

According to an embodiment, the mode information transmitted to thecontrol unit may be determined based on the signal reception result ofthe modem unit of the receiver. The modem unit may be positioned at theABB block output end.

FIG. 3B is a diagram illustrating a configuration of the terminalsupporting the first and second HB modes according to an embodiment ofthe present invention.

Referring to FIG. 3B, the terminal includes two first RF units 322 and324 for the first HB I/Q paths, two second RF units 326 and 328 for thesecond HB I/Q paths, two first ABB blocks 332 and 334 for the basebandI/Q paths corresponding to the first HB, two second ABB blocks 336 and338 for the baseband I/Q paths corresponding to the second HB, aswitching unit 330 connecting the RF units 322, 324, 326, and 328 to theABB blocks 332, 334, 336, and 328, and a control unit 340 forcontrolling the switching unit 330 according to the communication mode.

The first RF I unit 322 and the first RF Q unit 324 for the I path ofthe first HB are configured so as to operate as an RF unit for I or Qpath of the LB. Alternatively or additionally, the second RF I unit 326and the second RF Q unit 328 for the I path of the second HB may beconfigured so as to operate as the RF unit for the I or Q path of theLB. In the case that the terminal operates in the 2G mode, the first RFI/Q units 322 and 324 or the second RF I/Q units 326 and 328 areresponsible for receiving the RF signal and converts the RF signal tothe baseband I/Q signals. In the case that the terminal operates in the3G/4G mode, the first RF I/Q units 322 and 324 is responsible ofreceiving the RF signals of the first HB and converting the RF signalsto the baseband I/Q signals, and the second RF I/Q units 326 and 328 areresponsible for receiving the RF signals of the second HB and convertsthe RF signals to the baseband I/Q signals.

The ABB blocks 332, 334, 336, and 318 are configured to process the I/Qsignals corresponding to the first or the second HB independently or theI/Q signals corresponding to the LB in cooperation by two. In detail,the first ABB I block 332 and the first ABB Q block 334 operateindependently in the 3G/4G mode but they are configured to process the Isignal (or Q signal) of the LB in the 2G mode. Likewise, the second ABBQ block 336 and the second ABB I block 318 operate independently in the3G/4G mode but they are configured to process the Q signal (or I signal)of the LB in the 2G mode. The first ABB I/Q blocks 332 and 334 and thesecond ABB I/Q blocks 336 and 318 are arranged symmetrically toprocessing the I/Q signals cooperatively in the 2G mode. In detail, thesecond ABB Q block 336 is arranged close to the first ABB Q block 334such that the capacitor regions included in the first ABB I/Q blocks 332and 334 are connected to each other and the capacitor regions includedin the second ABB I/Q blocks 336 and 338 are connected to each other.

The switching unit 330 connects the RF units 322, 324, 326, and 328 tothe ABB blocks 332, 334, 336, and 318 according to the selectedcommunication mode under the control of the control unit 340. Thecontrol unit manages the overall operations of the terminal and controlsthe switching unit 330 depending on whether the communication mode isthe 2G mode or the 3G/4G mode. In detail, the switching unit 330connects the first RF I unit 322 to the first ABB I block 332, the firstRF Q unit 324 to the first ABB Q block 334, the second RF I unit 326 tothe second ABB I block 318, and the second RF Q unit 328 to the secondABB Q block 336.

If the first RF I/Q units 322 and 324 are configured to receive the RFsignals of the 2G LB in the 2G mode, the switching unit 330 connects thefirst RF Q unit 324 to the first ABB Q block 334, and the capacitorregion of the first ABB Q block 334 is extended to include the capacitorregion of the first ABB I block 332. For this extension, the capacitorregion of the first ABB Q block 334 is arranged close to the capacitorregion of the first ABB I block. The switching unit also connects thefirst RF I unit 322 to the second ABB Q block 336, and the second ABB Qblock 336 is extended to include the capacitor region of the second ABBI block 318. For this extension, the capacitor region of the second ABBQ block 336 is arranged close to the capacitor region of the second ABBI block 318.

In another embodiment, if the second RF I/Q units 326 and 328 areconfigured to receive the RF signals of the 2G LB in the 2G mode, theswitching unit 330 connects the second RF I unit 326 to the first ABB Qblock 334, and the capacitor region of the first ABB Q block 324 isextended to include the capacitor region of the first ABB I block 332.The switching unit 330 connects the second RF Q unit 328 to the secondABB Q block 336, and the capacitor region of the second ABB Q block 336is extended to include the capacitor region of the second ABB I block338.

According to an embodiment, the mode information transmitted to thecontrol unit may be determined based on the signal reception result ofthe modem unit of the receiver. The modem unit may be positioned at theABB block output end.

FIGS. 4A and 4B are a block diagram and a floor plan diagramillustrating the analog baseband filter according to an embodiment ofthe present invention.

Referring to FIG. 4A, the analog baseband filter includes a firstfiltering/amplifying path 410 for the I signal of the 3G/4G mode PRX HB,a second filtering/amplifying path 420 shared for the Q signal of thePRX HB and the I/Q signals of the LB, a third filtering/amplifying path430 shared for the Q signal of the DRX HB and the Q/I signals of the LB,and the fourth filtering/amplifying path 440 for the I signal of the DRXHB.

Each of the filtering/amplifying paths 410, 420, 430, and 440 includesan RP filter 412 connected to the positive input and negative inputs, afirst BQ filter 414, a second BQ filter 416, and a variable gainamplifier (VGA) 418 connected to the positive and negative outputs.

As described above, the filtering/amplifying paths 420 and 430 of theprimary Q channel and diversity Q channel are configured so as to beused for filtering/amplifying in the 2G mode. That is, thefiltering/amplifying paths 420 and 430 are shared for the primary anddiversity Q channels and the I and Q channels of the 2G mode. In anotherembodiment, the filtering/amplifying paths may be shared for theprimary/diversity I channels and the channels of the 2G mode and thismay be practiced by those skilled in the art based on the drawings andthe description made hereinafter.

The filtering/amplifying paths 430 and 420 of the diversity I and Qchannels are arranged across each other and thus thefiltering/amplifying path 430 of the diversity Q channel is positionedclose to the filtering/amplifying path 420 of the primary Q channel suchthat the I and Q channel paths of the 2G mode are arranged close evenwhen the filtering/amplifying paths 420 and 430 operate in the 2G mode.

FIG. 4B is a floor plan diagram illustrating the circuit correspondingto the analog baseband filtering/amplifying paths 410 to 440 of FIG. 4A.The drawing shows the connection relationship between the filter blocks460 to 474 corresponding to the filtering/amplifying paths and RF units452, 454, 456, and 458 and the internal arrangements of the respectivefilter blocks 460 to 474.

FIG. 4B shows the PRX RF I unit 452 and PRX RF Q unit 454 for the I andQ signals of the PRX HB and the DRX RF I unit 456 and DRX RF Q unit 458for the I and Q signals of the DRX HB. All or at least two of the PRX RFI and Q units 452 and 454 and the DRX I and Q units 456 and 458 areconfigured so as to be capable of processing the I and Q signals of the2G mode.

In the 3G/4G mode, the PRX RF I unit 452 receives the RF signal of thePRX HB, converts the RF signal to the baseband I signal, and sends the Isignal to the corresponding first filter block 460 and 462. The PRX RF Qunit 454 receives the Q signal of the PRX HB and sends the Q signal tothe corresponding second filter block 464 and 466, the DRX RF I unit 456receives the I signal of the DRX HB and sends the I signal to thecorresponding third filter block 468 and 470, and the DRX RF Q unit 458receives the Q signal of the DRX HB and sends the Q signal to the fourthfilter block 472 and 474. In the 2G mode, the PRX RF I and Q units 452and 454 or the DRX RF I and Q units 456 and 458 receives the RF signalsof the 2G LB, converts the RF signal to baseband I and Q signals, andsend the I and Q signals to the corresponding second and third filterblocks 464, 466, and 468, and 470; and the capacitor regions 464 and 470of the second and third filter blocks are extended to include thecapacitor regions of other neighboring filter blocks.

The filter blocks 460 to 474 are configured to be equivalent to thefiltering/amplifying units 410 to 440 of FIG. 4A. The first filter blockis made up of the active region 460 including a resistor and activedevices such as OP AMP and a capacitor region 462 including capacitorsand equivalent to the first filtering/amplifying path 410 of FIG. 4A.The second filter block is made up of a capacitor region 464 and anactive region 466 and equivalent to the second filtering/amplifying path420 of FIG. 4A. The capacitor region 464 of the second filter block isarranged close to the capacitor region 462 of the first filter block soas to be connected to the capacitor region 462 of the first filter blockin the 2G mode, resulting in extension of the capacitance. The thirdfilter block is made up of an active region 468 and a capacitor region470 and equivalent to the third filtering/amplifying path 430 of FIG.4A. The fourth filter block is made up of a capacitor region 472 and anactive region 474 and equivalent to the fourth filtering/amplifying path440 of FIG. 4A. The capacitor region 470 of the third filter block isarranged close to the capacitor region 472 of the fourth filter block soas to be connected to the capacitor region 472 of the fourth filterblock in the 2G mode, resulting in extension of capacitance.

As described above, the capacitor regions of two filter blocks arearranged close each other so as to be connected to make it possible toprocess the signals of the 2G mode.

FIGS. 5A to 5C are diagrams illustrating the mode switching of theanalog filter according to an embodiment of the present invention. Indetail, FIG. 5A shows the signal flows in the 3G/4G mode, FIG. 5B showsthe signal flows in the case that the PRX RF I and Q units 452 are usedin the 2G mode, and FIG. 5C shows the signal flows in the case that theDRX RF I and Q units 456 and 458 is used in the 2G mode.

Referring to FIG. 5A, the PRX RF I unit 452 receives the RF signal ofthe PRX HB, down-converts the RF signal to a baseband I signal, andsends the I signal to the first filter block 460 and 462; and the activeregion 460 and the capacitor region 462 of the first filter blockoperate for processing the I signal of the PRX HB. The PRX RF Q unit 454receives the RF signal of the PRX HB, down-converts the RF signal to abaseband Q signal, and sends the Q signal to the second filter block 464and 466; and the capacitor region 464 and the active region 466 of thesecond filter block operate for processing the Q signal of the PRX HB.

The DRX RF I unit 456 receives the RF signal of the DRX HB,down-converts the RF signal to a baseband I signal, and sends the Isignal to the fourth filter block 472 and 474; and the capacitor region472 and the active region 474 of the fourth filter block operate forprocessing the I signal of the DRX HB. The DRX RF Q unit 458 receivesthe RF signal of the DRX HB, down-converts the RF signal to a baseband Qsignal, and sends the Q signal to the third filter block 468 and 470;and the active region 468 and the capacitor region 470 of the thirdfilter block operate for processing the Q signal of the DRX HB.

As described above, the PRX and DRX paths operate independently in the3G/4G mode such that the outputs of the RF units 452, 454, 456, and 458are sent to the corresponding filter blocks 460 to 474 by means of theswitching unit 500.

As shown in FIGS. 5B and 5C, the input signals are sent to the PRX RFunits 452 and 454 or the DRX RF units 456 and 458 in the 2G mode so asto achieve universality. In the case of using the PRX RF units 452 and454 in the 2G mode, the DRX RF units 456 and 458 are turned off tominimize unnecessary power consumption. In contrast, the PRX RF units452 and 454 are turned off to minimize the unnecessary power consumptionin the case of using the DRX RF units 456 and 458 in the 2G mode.

For the filter inputs from the PRX RF units 452 and 454, the switchingunit 510 establishes channels between the PRX RF units 452 and 454 andsome regions 462 to 472 of the filter blocks as shown in FIG. 5B.

In detail, the PRX RF I unit 452 receives the RF signal of the LB,down-converts the RF signal to a baseband I signal, and sends the Isignal to the third filter block 468 and 470 via the switching unit 510;and the capacitor region 472 of the third filter block is connected tothe capacitor region 472 of the fourth filter block such that the activeregion 468 and the capacitor region 470 of the third filter block andthe capacitor region 472 of the fourth filter block operate forprocessing the I signal of the LB. At this time, the variable capacitorsincluded in the capacitor region 472 of the fourth filter block arecontrolled by means of the control signal of the active region 468 ofthe third filter block. The active region 474 of the fourth filter blockmay enter the idle state to minimize unnecessary power consumption.

The PRX RF Q unit 454 receives the RF signal of the LB, down-convertsthe RF signal to a baseband Q signal, and sends the Q signal to thesecond filter block 464 and 466; and the capacitor region 464 of thesecond filter block is connected to the capacitor region 462 of thefirst filter block such that the capacitor region 462 of the firstfilter block and the capacitor region 464 and active region 466 of thesecond filter block operate for processing the Q signal of the LB. Atthis time, the variable capacitors included in the capacitor region 462of the first filter block are controlled by means of the control signalof the active region 466 of the second filter block. The active region460 of the first filter block may enter the idle state to conservepower.

For the filter inputs from the DRX RF units 456 and 458, the switchingunit 520 establishes channels between the DRX RF units 456 and 458 andsome regions 462 to 472 of the filter blocks as shown in FIG. 5C.

In detail, the DRX RF I unit 456 receives the RF signal of the LB,down-converts the RF signal to a baseband I signal, and sends the Isignal to the second filter block 464 and 466 via the switching unit520; and the capacitor region 464 of the first filter block is connectedto the capacitor region 462 of the first filter block such that thecapacitor region 462 of the first filter block and the capacitor region464 and active region 466 of the second filter block operate forprocessing the I signal of the LB. At this time, the active region 460of the first filter block may enter the idle state to conserve power.

The DRX RF Q unit 458 receives the RF signal of the LB, down-convertsthe RF signal to a baseband Q signal, and sends the Q signal to thethird filter block 468 and 470; and the capacitor region 470 of thethird filter block is connected to the capacitor region 472 of thefourth filter block such that the active region 468 and capacitor region470 of the third filter block and the capacitor region 472 of the thirdfilter block operate for processing the Q signal of the LB. At thistime, the active region 474 of the fourth filter block may enter theidle state to conserve power.

As described above, the capacitors on the neighbor path are connected tothe capacitors on the signal path for the 2G mode in parallel so as tosecure extended capacitance for processing the signal of the 2G mode. Asa consequence, it is possible to receive the low band signal efficientlyusing the extended capacitance.

The frequency range may be extended up to three times by controllingindividual capacitor banks to make it possible to support the frequencyrange of up to 6 times through capacity sharing. In addition, byreplacing the resistors constituting the analog filter with fourresistor segments connected in series and parallel, it is possible toincrease the resistance up to 16 times. In this way, the frequency rangeis extended up to 96 times.

FIG. 6 is a circuit diagram illustrating a resister block varying inresistance depending on the operation mode according to an embodiment ofthe present invention. The resistor block may substitute for at leastone of the input resistor Ra and the feedback resistor Rb constitutingan analog filter and controlled depending on the gain, cutoff frequency,or operation mode.

Referring to FIG. 6, the resister block 600 includes four variableresistor segments 602, 604, 606, and 608 connected between the inputterminal R_(in) and the output terminal R_(out) in parallel, the inputnodes of resistor segments 602 to 608 are connected to the inputterminal by means of the switches SW1 to SW4, and the output nodes ofthe resistor segments 602 to 608 are connected to the output terminal bymeans of the switches SW8 to SW13. The switch SW9 is interposed betweenthe output nodes of the first and resistor segments 602 and 604, theswitch SW6 between the input nodes of the second and third resistorsegments 604 and 606, and the switch SW12 between the output nodes ofthe third and fourth resistor segments 606 and 608. The switch SW5 isarranged in parallel with the resistor segments 602 to 608, and theswitch SW7 is interposed between the input node of the fourth resistorsegment 608 and the output node of the switch SW5.

Assuming that each resistor segment has the resistance of Rx, theswitches SW1 to SW13 are controlled depending on the gain, cutofffrequency, and operation mode such that the total resistance of theresistor block varies in the range from ¼ to 4 times the Rx.

In the embodiment of FIG. 6, only the switches SW1 to SW8 are on whilethe others are off. Accordingly, the total resistance becomes Rx by thefirst resistor segment 602. Likewise, the total resistance of theresistor block can be controlled within the range of ¼ to 4 times of Rxby through on/off control of the switches.

FIGS. 7A to 7F are circuit diagrams illustrating various configurationsof the resistor block according to an embodiment of the presentinvention.

FIG. 7A shows the resistor block configured for the mode 1 forprocessing LB signals such as 2G mode in which the four resistorsegments 702 are connected in series by means of the switches SW1, SW9,SW 6, SW 12, and SW 7 while other switches are off such that the totalresistance becomes 4Rx.

FIG. 7b shows the resistor block configured for mode 2 in which thethird and fourth resistor segments 704 are connected in series by meansof the switches SW3, SW12, and SW7 while the other switches are off suchthat the total resistance becomes 2Rx.

FIG. 7C shows the resistor block configured for mode 3 in which only thefirst resistor segment 706 connects the input and output terminals bymeans of the switches SW1 and SW8 while other switches are off such thatthe total resistance becomes Rx.

FIG. 7D shows the resistor block configured for mode 4 in which thethird and fourth resistor segments 708 are connected in parallel betweenthe input and output terminals by means of the switches SW3, SW11, SW4,and SW13 while other switches are off such that the total resistancebecomes 0.5Rx.

FIG. 7E shows the resistor block configured for mode 5 in which the fourresistor segments 710 are connected in parallel between the input andoutput terminals by means of the switches SW1, SW2, SW3, SW4, SW8, SW10,SW11, and SW13 while other switches are off such that the totalresistance becomes ¼Rx.

FIG. 7F shows the resistor block configured for mode 6 in which allswitches are off with the exception of the switch SW5 such that theinput and output terminal are connected directly without interpositionof the resistor segments 712.

The Rx of the unit resistor segment is determined variably depending onthe gain required by each filter and, since the typically intended gainrange is −12˜+24 dB, the ratio between the input resistor segments andthe feedback resistor segments.

FIG. 8 is a circuit diagram illustrating a configuration of the analogbaseband filter according to an embodiment of the present invention.

Referring to FIG. 8, the analog baseband filter includes four filterblocks 808 a, 808 b, 808 c, and 808 d; and the DRX I and Q signals andPRX Q and I signals are input to the input switching unit 806 via therespective frequency convertors 802 and amplifiers 804. The inputswitching unit 806 relays the input signals to at least two of thefilter blocks 808 a to 808 d depending on the current communication modeunder the control of a control unit (not shown). In the 3G/4G mode, theinput switching unit 806 relays the 4 input signals to the four filterblocks 808 a to 808 d. In the 2G mode, the input switching unit 806delivers the 2G I and Q signals input from the DRX RF unit through theDRX I and Q input nodes to the second and third filter blocks 808 b and808 c, i.e., the 2G Q signal from the DRX RF Q unit to the second block808 b and the 2G I signal from the DRX RF I unit to the third filterblock 808 c. In another embodiment, in the 2G mode, the input switchingunit 806 relays the 2G I and Q signals input from the PRX RF unitthrough the PRX I and Q input nodes to the second and third filterblocks 808 b and 808 c, i.e. the 2G Q signal from the PRX RF Q unit tothe third filter block 808 c and the 2G I signal from the PRX RF I unitto the second filter block 808 b.

The first filter block 808 a is described as a representative filterblock hereinafter. The first filter block 808 a includes three filterstages (i.e. RF filter 810, BQ first filter 812, and second BQ filter814) and an amplifier stage 816. The filter stages 810, 812, and 814 ofthe first filter block 808 a operate alone in the 3G/4G mode but are notconnected to the filter stages of the second filter block 808 b. In the2G mode, the capacitors C1 of the RP filter 810 cuts of its connectionto the OP AMP A and connects to the capacitors Clx included in the RPfilter of the second filter block 808 b in parallel, and the OP AMP Aturns off. Likewise, in the 2G mode, the capacitors C2, C3, C4, and C5of the next filter stages 812 and 814 cuts off their connection to theOP AMPs B, C, D, and E and connect to the capacitors C2 x, C3 x, C4 x,and C5 x corresponding to the second filter block 808 b in parallel.

The output signals of the filter blocks 808 a to 808 d are delivered tothe corresponding output terminals through the output switching unit 818under the control of the control unit. In the 3G/4G mode, the outputswitching unit 818 delivers the output signals from the filter blocks808 a to 808 d to the respective DRX I output, DRX Q output, PRX Qoutput, and PRX I output nodes. In the 2G mode, the output switchingunit 818 delivers the output signal from the third filter block 808 c tothe 2G I output node and the output signal from the second filter block808 b to the 2G Q output.

FIGS. 9A and 9B are circuit diagrams illustrating detailed arrangementof the capacitors according to an embodiment of the present invention.

Referring to FIG. 9A, the first OP AMP 902 is positioned in the firstfilter block 808 a and connected to the two capacitors C11 and C21 inparallel. The second OP AMP 904 is positioned in the second filter block808 b and connected to the two capacitors C12 and C22 in parallel. Thecapacitor C11 is connected in parallel with the first OP AMP 902 bymeans of the switches SW1 and SW2, the switch SW3 is interposed betweenthe input nodes of the capacitors C11 and C12, and the switch SW4 isinterposed between the output nodes of the capacitors C11 and C12.Likewise, the capacitor C21 is connected in parallel with the second OPAMP 902 by means of the switches SW5 and SW6, the switch SW7 isinterposed the input nodes of the capacitors C21 and C22, and the switchSW8 is interposed between the output nodes of the capacitors C21 andC22.

In the 3G/4G mode, the switches SW1, SW2, SW5, and SW6 interposedbetween the capacitors C11 and C21 are on (i.e. closed) while theswitches SW3, SW4, SW7, and SW8 interposed between the capacitors C11and C12 and between C21 and C22 are off (i.e. opened). Accordingly, thecapacitors operate in the corresponding filter blocks.

Referring to FIG. 9B, in the 2G mode, the switches SW3, SW4, SW7, andSW8 interposed between the capacitors C11 and C12 and between thecapacitors C21 and C22 of different filter blocks are on while theswitches SW1, SW2, SW5, and SW6 interposed between the capacitors C11and C21 of the first filter block 808 a and the OP AMP 902 are off.Accordingly, the capacitors C11 and C21 operate in the state of beingconnected in parallel with the OP AMP 904 of the second filter block 808b other than the first filter block 808 a. At this time, the OP AMP 904of the first filter block 808 a may be off to conserve the power. Bycontrolling the other filter stages and capacitors of other filterblocks similarly depending on the communication mode, they can be sharedin both the 2G mode and 3G/4G mode.

FIGS. 10A to 10C are diagrams illustrating the operation mechanisms ofthe filter according to an embodiment of the present disclosure. Indetail, the drawings show the operations of the filter disclosed in thepresent invention when at least two signals are input. According to anembodiment, if at least two signals are input, the filter can be used incommunication with a communication entity operating in the CarrierAggregation (CA) mode.

Referring to FIGS. 10a to 10C, the filter module according to anembodiment of the present invention may include at least one of thefirst switching unit 1040, 1050, and 1060, the filtering unit 1002 and1022, and the second switching unit 1042, 1052, and 1062. The filteringunit may include at least one filter structured as shown in one of FIGS.5a to 5c and, in this embodiment, two corresponding filters areincluded. The first and second filters 1002 and 1022 are configuredcorrespondingly and may perform HB and LB filtering through capacitorsharing as described in the embodiments of the present invention.

In more detail, the filtering unit may include the first filter 1002 and1022. According to an embodiment, the filtering unit 1002 and 1022 maybe positioned on the same path. The first filter 1002 may include a PRXfilter 1004 for filtering HB PRX I and Q signals and a DRX 1 filteringunit 1010 for filtering the first DRX (DRX1) I and Q signals. The secondfilter 1022 may include a DRX 2 filtering unit 1024 for filtering thesecond DRX (DRX 2) I and Q signals and an SRX filtering unit forfiltering the second primary (SRX) I and Q signals. The signals areproposed for describing the embodiment, and the filter may filtervarious signals according to an embodiment of the present invention. Inan embodiment, the filtering units 1004, 1010, 1024, and 1030 mayinclude corresponding I path filtering units 1006, 1014, 1026, and 1032and corresponding Q filtering units 1004, 1012, 1028, and 1030.

In an embodiment, filtering units may filter the HB input signals inputthrough the I and Q paths and share the capacitors of the I and Qfiltering units to filter the LB input signals. In an embodiment, onlythe filters on one path for the LB filter and, although Q path isactivated in the embodiment for explanation, it is possible to activatethe I path for filtering the LB signal. In an embodiment, the filteringunit for filtering on each path may be designed such that capacitors canbe shared effectively.

The filters of FIGS. 10A to 10C may receive a plurality signals. In anembodiment, it may be considered that a plurality signals are receivedin the communication system operating in the Carrier Aggregation (CA)mode. In an embodiment, the filter may receive a plurality of LB signals(e.g. 2G signals). The plural LB signals may be the 2G signals receivedin the CA mode. In an embodiment, the carrier-aggregated signals may bereceived through an antenna unit (not shown), and the module may controlthe first switching unit 1040, 1050, and 1060 and the second switchingunit 1042, 1052, and 1062 to send the signals to the filtering unit. Inan embodiment, the first switching unit 1040, 1050, and 1060 may performswitching to send the received signal to the activated Q path filteringunits 1008, 1012, 1028, and 1032. The second switching unit 1042, 1052,and 1062 may perform switching to send the filtered signal topreconfigured ports.

FIG. 10A is directed to an embodiment where a plurality of LB signalsare received through PRX and SRX ports. The first switching unit 1040may be controlled to send the signals to the Q path filtering units1008, 1012, 1028, and 1030. The first switching unit 1040 may becontrolled depending on the signal reception result of a modem (noshown). The second switching unit 1042 may be controlled to send thesignals filtered by the Q path filtering units 1008, 1012, 1028, and1030 to preconfigured ports.

FIG. 10B is directed to an embodiment where a plurality of LB signalsare received through PRX and DRX 1 ports. The first switching unit 1050may be controlled to send the signals to the Q path filtering units1008, 1012, 1028, and 1030. The first switching unit may be controlleddepending on the signal reception result of a modem (not shown). Thesecond switching unit 1052 may be controlled to send the signalsfiltered by the Q path filtering units 1008, 1012, 1028, and 1030 topreconfigured ports.

FIG. 10C is directed to an embodiment where a plurality of LB signalsare received through DRX 2 and SRX ports. The first switching unit 1060may be controlled to send the signals to the Q path filtering units1008, 1012, 1028, and 1030. The first switching unit 1060 may becontrolled depending on the signal reception result of a modem (notshown). The second switching unit 1062 may be controlled to send thesignals filtered by the Q path filtering units 1008, 1012, 1028, and1030 to preconfigured ports.

Although the description has been directed to the control methoddepending on the scenario of receiving a plurality of signals, thefiltering can be performed in such a way of controlling the switchingunit in order for the activated filtering unit to receive the signalstransmitted in a method not described in the disclosure.

As described above, a plurality of filtering units having the filterscapable of filtering low band signals through capacitors sharing iscapable of filtering signals transmitted in carrier aggregation mode.

As described above, the embodiments of the present invention providereceiver systems and digital control code that are capable of sharingcapacitor regions for diversity path of the 3G/4G mode, enhancing theinput and feedback resistors structure and changing the input and outputpaths depending on the communication mode. According to variousembodiments of the present invention, it is possible to provide avarious gain amplifier, filter circuit, and algorithm that is capable ofachieving the gain and bandwidth required at the baseband receiver forall the mobile communication standards supported in 2G, 3G, and 4Gsystems.

Also, the embodiments of the present invention is capable of reducingthe circuit area by over half as compared with the conventionaltechnology and applying efficiently to accomplish the MIMO receiverconfiguration such as 4×2, 4×4, and 8×4 antenna configurations in thenext generation mobile communication technologies.

As described above, the analog signal filtering apparatus and method ofthe present invention is advantageous in terms of providing a variablegain amplifier, filter circuit, and algorithm capable of fulfilling thegains and bandwidths required by the baseband receiver for all mobilecommunication standards complied by 2G, 3G, and 4G systems.

Also, the analog signal filtering apparatus and method of the presentinvention is advantageous in terms of implementing the various circuitstructures capable of decreasing manufacturing costs and enhancing noisecancellation by decreasing the circuit area as compared to theconvention technologies and facilitating application of Multiple InputMultiple Output (MIMO) receiver configurations such as 4×2, 4×4, and 8×4antenna configurations.

Also, the analog signal filtering apparatus and method of the presentinvention is advantageous in terms of providing a filter circuit forcommunication circuit design supporting Carrier Aggregation (CA) for useof carriers on multiple frequency bands.

Although preferred embodiments of the invention have been describedusing specific terms, the specification and drawings are to be regardedin an illustrative rather than a restrictive sense in order to helpunderstand the present invention. It is obvious to those skilled in theart that various modifications and changes can be made thereto withoutdeparting from the broader spirit and scope of the invention.

The invention claimed is:
 1. A filtering apparatus of a multimodemultiband radio transceiver, the apparatus comprising: a filter whichfilters Radio Frequency (RF) signals on one of at least one frequencybands; a switch which switches the RF signals among a plurality offilter blocks included in the filter according to a selectedcommunication mode; and at least one processor which selects thecommunication mode and controls the switch, wherein a first filter blockof the plurality of filter blocks is configured to be connectable to acapacitor of a second filter block of the plurality of filter blocks. 2.The apparatus of claim 1, wherein the filter comprises at least one RFreceiver which receives the RF signals as input and outputs basebandsignals, wherein at least one filter block of the plurality of filterblocks filters and amplifies the baseband signals, and wherein theswitch connects at least two of the at least one RF receiver to the atleast one filter block.
 3. The apparatus of claim 2, wherein a capacitorof the first filter block of the at least one filter block is arrangedclose to the capacitor of the second filter block.
 4. The apparatus ofclaim 2, wherein the at least one RF receiver comprises at least one RFreceiver which outputs In Phase (I) and Quadrature Phase (Q) signalscorresponding to a RF signal of a primary High Band (HB) among frequencybands in a first communication mode and outputs I and Q signalscorresponding to a RF signal of a Low Band (LB) among frequency bands ina second communication mode.
 5. The apparatus of claim 4, wherein thecapacitor of the first filter block shares active devices of the secondfilter block close thereto in the second communication mode, the activedevices being turned off.
 6. The apparatus of claim 5, wherein the atleast one processor activates the first and second filter blocks incorrespondence to the second communication mode when the at least one RFreceiver receives RF signals on at least two LBs, and the switchperforms switching to transfer the signals received by the RF receiverto the activated filter blocks.
 7. The apparatus of claim 6, furthercomprising an output switch which connects the signals output from theactivated filter blocks to a specific output port.
 8. A method forcontrolling a filtering apparatus of a multimode multiband radiotransceiver, the method comprising: receiving, at a filter including aplurality of filter blocks, a Radio Frequency (RF) signal on at leastone frequency band; determining a communication mode based on thereceived signal; switching the received signal among the plurality offilter blocks included in the filter according to the communicationmode; and filtering and amplifying, at the filter, the received signal,wherein a first filter block of the plurality of filter blocks isconfigured to be connectable to a capacitor of a second filter block ofthe plurality of filter blocks.
 9. The method of claim 8, wherein thefilter comprises at least one RF receiver which receives RF signals asinput and outputs baseband signals, at least one filter block of theplurality of filter blocks filters and amplifies the baseband signals,the switch connects at least two of the at least one RF receiver to theat least one filter block.
 10. The method of claim 9, wherein acapacitor of the first filter block of the plurality of filter blocks isarranged close to the capacitor of the second filter block.
 11. Themethod of claim 9, wherein the at least one RF receiver comprises atleast one RF receiver which outputs In Phase (I) and Quadrature Phase(Q) signals corresponding to a RF signal of a primary High Band (HB)among frequency bands in a first communication mode and outputs I and Qsignals corresponding to a RF signal of a Low Band (LB) among frequencybands in a second communication mode.
 12. The method of claim 11,wherein the capacitor of the first filter block shares active devices ofthe second filter block close thereto in the second communication mode,the active devices being turned off.
 13. The method of claim 11, furthercomprising: activating, at at least one processor, the first and secondfilter blocks in correspondence to the second communication mode whenthe at least one RF receiver receives RF signals on at least two LBs;and switching, at the switch, the signals received by the RF receiver tothe activated filter blocks.
 14. The method of claim 13, furthercomprising connecting signals output from the activated filter blocks toa specific output port by controlling an output switch.